What are they?

[Donewiththisplace]

The white tubes..

 

[trinimaddness]

i believe tube worms

 

[SantaMonica]

Beautiful. And sometimes you'll fine super tiny tube-tree like structures, which are foraminifera.

 

[ZippysFunLand]

Definitely tube worms. If you are concerned about them, a quick google search will come up with lots of non reef safe fish that will eradicate them from your tank. For me, I have plenty of coral in my tank and I'm not comfortable with putting any of these rock nipping fish in my reef.

 

[Donewiththisplace]

Not really concerned too much with them...this rock had the majority of them, which I removed. There are some spread throughout the tank but not to the point where I'm gonna do something about them.

I'll monitor for now. Thanks.